Method for Manufacturing a Diagnostic Test Strip

ABSTRACT

A method for manufacturing a diagnostic test strip is disclosed according to one embodiment. The method includes the acts of providing an application sheet having a plurality of adhesive dots thereon, providing a first substrate layer having at least one feature located thereon, and providing a second substrate layer. The method further including the acts of transferring at least one of the plurality of adhesive dots located on the application sheet to the first substrate layer, aligning the first substrate layer with the second substrate layer, and attaching the first substrate layer and the second substrate layer using the transferred adhesive dots, wherein the attaching of the first and second substrate layers is performed without any additional alignment.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Application No. 60/571,046 filed onMay 14, 2004, which is incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to diagnostic instruments and,more particularly, to a method for manufacturing a diagnostic test stripfor use in determining the concentration of an analyte in a liquidsample.

BACKGROUND OF THE INVENTION

Test strips (e.g., biosensors) containing reagents are often used inassays for determining the analyte concentration in a fluid sample.Testing and self-testing for the concentration of glucose in blood is acommon use for test strips. Typical diabetic users test themselvesbetween one to four times daily. Each test requires that a new testsensor be used and, thus, cost of the individual test sensors isimportant to the users.

Test sensors can be manufactured by attaching multiple layers togetherto form a single test sensor. In the manufacturing of multi-layered testsensors, typically an adhesive is applied between the layers to ensurethat the layers remain securely attached. These attached layers are thenpunched to create the features (e.g., capillary channels, reactionareas, electrodes, test elements, etc.) required for the test sensor tofunction as desired. However, the punching of the attached layers causesthe adhesive to build-up around the punching or slitting dies. Thisbuild-up requires the manufacturing apparatus be shut down periodicallyto remove the accumulated adhesive around the dies, which incurssignificant costs and time. Additionally, alignment of the adhesive withthe layers to be attached generally requires precise alignment of theadhesive with the first layer and then alignment of a first layer andadhesive with a second layer.

Test sensors can also be manufactured by attaching embossed layerstogether to form a single test sensor. Typically, one side of anadhesive layer is attached to an embossed base layer. A third layer isthen applied to the other side of the adhesive layer, opposite the baselayer. This requires the manufacturer to first align the embossed baselayer with the adhesive layer to avoid the covering of the embossedfeatures by the adhesive layer. Then the manufacturer must align thethird layer with the newly formed base-adhesive layered structure. Thisprocedure is then repeated with additional layers are added to thestructure.

Thus, a need exists for a new method of manufacturing a test sensor.

SUMMARY OF THE INVENTION

A method for manufacturing a diagnostic test strip is disclosedaccording to one embodiment of the present invention. The methodincludes the acts of printing a plurality of adhesive dots on a firstsurface of a provided application sheet. A feature is fashioned into aface at least one of a plurality of substrate layers. The applicationsheet is then applied to one of the plurality of substrate layers suchthat the adhesive dots are located between the application sheet and thefirst substrate layer. At least one adhesive dot is transferred from theapplication sheet to the first substrate layer by removing theapplication sheet from the first substrate layer. The first substratelayer is then aligned with another of the plurality of substrate layers.The second substrate layer is applied to the first substrate layer, suchthat the transferred adhesive dots are in contact with both the firstsubstrate layer and the second substrate layer.

A method for manufacturing a diagnostic test strip is disclosedaccording to another embodiment of the present invention. The methodincludes the acts of applying an adhesive to a plurality of differentareas on a first surface of a provided application sheet. A feature isfashioned into a face at least one of a plurality of substrate layers.The feature creates an uppermost surface and a lowermost surface on theface of the first substrate layer. The application sheet is then appliedto the first substrate layer such that the adhesive is located betweenthe first surface of the application sheet and the face of the firstsubstrate layer. At least one of the plurality of different areas of theadhesive is in contact with the uppermost surface of the face of thefirst substrate layer. The adhesive is transferred by removing theapplication sheet from the first substrate layer after at least one ofthe plurality of different areas of the adhesive is in contact with theuppermost surface of the face of the first substrate layer, such thatthe adhesive in contact with the uppermost surface of the face of thefirst substrate layer remains. A second plurality of substrate layers isthen aligned with the first substrate layer and the second substratelayer is applied to the first substrate layer. The adhesive remaining onthe uppermost surface of the face of the first substrate layer contactsboth the first substrate layer and the second substrate layer.

A method for manufacturing a diagnostic test strip is disclosedaccording to another embodiment of the present invention. The methodincludes the acts of providing an application sheet having a pluralityof adhesive dots thereon, providing a first substrate layer having atleast one feature located thereon, and providing a second substratelayer. The method further including the acts of transferring at leastone of the plurality of adhesive dots located on the application sheetto the first substrate layer, aligning the first substrate layer withthe second substrate layer, and attaching the first substrate layer andthe second substrate layer using the transferred adhesive dots, whereinthe attaching of the first and second substrate layers is performedwithout any additional alignment.

The above summary of the present invention is not intended to representeach embodiment, or every aspect, of the present invention. Additionalfeatures and benefits of the present invention are apparent from thedetailed description, figures, and claims set forth below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is an exploded side view of an application sheet and asubstrate layer according to one embodiment of the present invention.

FIG. 1 b is a side view of the application sheet of FIG. 1 a removablyattached to the substrate layer of FIG. 1 a.

FIG. 1 c is a side view of the substrate layer of FIG. 1 b after theapplication sheet has been removed.

FIG. 2 is an exploded side view of an application sheet and a substratelayer according to one embodiment of the present invention.

FIG. 2 b is a side view of the application sheet of FIG. 2 a removablyattached to the substrate layer of FIG. 2 a.

FIG. 2 c is a side view of the substrate layer of FIG. 2 b after theapplication sheet has been removed.

FIG. 3 is an exploded perspective view of an example of a test sensorcapable of being manufactured according to one embodiment of the presentinvention.

FIG. 4 is a flowchart of a method for adhering a first substrate layerto a second substrate layer according to one embodiment of the presentinvention.

While the invention is susceptible to various modifications andalternative forms, specific embodiments are shown by way of example inthe drawings and are described in detail herein. It should beunderstood, however, that the invention is not intended to be limited tothe particular forms disclosed. Rather, the invention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the invention as defined by the appended claims.

DESCRIPTION OF ILLUSTRATED EMBODIMENTS

Turning now to the drawings and initially to FIGS. 1 a-c, a process 10for applying an adhesive 12 to a substrate layer 14 is shown accordingto one embodiment of the present invention. The substrate layer 14 has aface 17 where punched areas 15 have been formed by a prior process. Theadhesive 12 is originally attached to an application sheet 16 having theadhesive 12 located in separate and distinct areas. The applicationsheet 16 may be constructed of a silicon-treated substrate, which allowsfor the easy removal of the adhesive 12 from the application sheet 16.The adhesive 12 applied to the application sheet 16 is a transferablepressure-sensitive adhesive.

As shown in FIG. 1 a, the adhesive 12 is applied to the applicationsheet 16 to form a plurality of adhesive dots 13. The adhesive dots 13are applied to the application sheet 16, for example, by printing thedesired pattern thereon. In an embodiment where the adhesive dots 13 areprinted onto the application sheet 16, the adhesive 12 may be, forexample, a commercially-available adhesive, such as the dot matrixadhesive sold by Landerink, Inc. of Belmont, Mich. Though smalleradhesive dots 13 are desirable according to certain embodiments of thepresent invention, the size of the dots can be adjusted to be larger orsmaller. According to one embodiment of the invention, the adhesive dots13 are about 300 microns in diameter. The adhesive dots 13 may be formedin a variety of shapes, including but not limited to, circles, ovals,squares, rectangles, triangles, or other polygonal and non-polygonalshapes.

In FIG. 1 b, the application sheet 16 has been applied to the substratelayer 14 by applying pressure between the application sheet 16 and thesubstrate layer 14. As illustrated in FIG. 1 b, certain adhesive dots 13a are located between and in contact with both the application sheet 16and a face 17 of the substrate layer 14. At the same time, otheradhesive dots 13 b are located in the punched areas 15 and do notcontact the face 17 of the substrate layer 14. Upon removing theapplication sheet 16 from the substrate layer 14, the adhesive dots 13 apreviously in contact with the face 17 of the substrate layer 14 remainthereon, as shown in FIG. 1 c. The adhesive dots 13 a remain on the faceof the substrate layer 14 due to the higher adhesion forces between theadhesive 12 and the face 17 of the substrate layer 14 than between theadhesive 12 and the application sheet 16.

Referring now to FIGS. 2 a-c, a process 18 for applying an adhesive 12to a substrate layer 20 is shown according to another embodiment of thepresent invention. The face 21 of the substrate layer 20 has embossedareas 22, which have been formed by a prior process. As described abovein FIGS. 1 a-c, the application sheet 16 is applied to the face 21 ofthe substrate layer 20, as shown in FIG. 2 b. The adhesive dots 13 a arelocated between and in contact with both the application sheet 16 andthe face 21 of the substrate layer 20, while other adhesive dots 13 bare located in the embossed areas 22 and do not contact the face 17 ofthe substrate layer 20. Upon removing the application sheet 16 from thesubstrate layer 20, the adhesive dots 13 a previously in contact withthe face 21 of the substrate layer 20 remain on the face 21, as can beseen in FIG. 2 c.

Referring to FIG. 3, an example of an electrochemical test strip 30 isshown that is capable of being manufactured according to one embodimentof the present invention. The electrochemical test strip 30 is describedin greater detail in U.S. Pat. No. 6,531,040 B1 (“Electrochemical-SensorDesign”), which is incorporated herein by reference in its entirety. Thetest strip 30 may be used to determine the analyte concentration in atest fluid. The test strip 30 has a base 32 that is printed with variousinks to form a conductive element 34, which is overcoated with a workingelectrode 36 and a counter electrode 38. The base is then overcoatedwith a dielectric layer 40 that contains an opening 42 that determinesthe extent to which the working 36 and counter 38 electrodes are exposedto the test fluid. A reaction layer 44 overcoats the dielectric layer40. The dielectric layer 40 is printed with a predetermined patterndesigned to leave a desired surface of the electrodes 36,38 exposed tothe reaction layer 44 when it is printed over the dielectric layer 40.Finally, the base 32 is attached to a lid 46. The lid 46 is providedwith an embossed concaved space 48 on a lower side 49 of the lid 46. Thelid 46 is further provided with a venting hole 50.

The lid 46 and base 32 are then sealed together by, for example,utilizing an adhesive to form the electrochemical test strip 30. Theapplication sheet 16 (FIGS. 1-2) is applied to the lower side 49 of thelid 46 by applying a slight pressure to the application sheet 16. Asdescribed with respect to FIGS. 1-2, the adhesive dots 13 will makecontact with the flat, non-embossed regions of the lid 46. Thus, theadhesive 12 is not in contact with the concaved space 48 or the ventinghole 50. Upon removal of the application sheet 16, the adhesive dots 13that were in contact with the non-embossed portions of the lid 46 remainon the lid 46. The lid 46, with the adhesive dots 13 applied, is thenaligned with the base 32 and the lid 46, which are attached by applyinga slight pressure. The adhesive dots 13 fuse the base 32 to the lid 46to create the electrochemical test strip 30.

FIG. 4 is a flow diagram illustrating a method 60 of adhering a firstsubstrate layer to a second substrate layer, according to one embodimentof the present invention. At step 62, the adhesive 12 is applied to theapplication sheet 16 to form adhesive dots 13 (FIGS. 1-2). At step 64,at least a first substrate layer is fashioned by being punched orembossed to create the desired features thereupon. A plurality ofsubstrate layers may be fashioned at step 64 to form the particular teststrip being manufactured. After the desired features have been fashionedon the substrate layer(s), the application sheet 16 is applied to thefirst substrate layer at step 66. Pressure is applied to the applicationsheet 16 to ensure that the adhesive dots 13 are in contact with theuppermost surfaces of the first substrate layer. Once the adhesive dots13 have contacted the uppermost surfaces, the application sheet 16 isremoved, at step 68, while the adhesive dots 13 in contact with thesubstrate surfaces remain.

After the adhesive dots 13 have been applied to the first substratelayer, a second substrate layer is aligned with the first layer at step70. The second substrate layer is then applied to the first substratelayer, at step 72, and pressure is applied to ensure that the adhesivedots 13 are in contact with both the first and second substrate layers.Steps 64-74 may be repeated as many times as are necessary to attachfurther layers to the first, second, and/or additional substrate layers.

The method illustrated above has been described according to oneembodiment with the desired features being fashioned into the varioussubstrate layers prior to applying an adhesive to the first substratelayer. According to other embodiments of the present invention, however,the individual layers may be fashioned at any time prior to attachment,including after the adhesive has been applied to the first substratelayer, the second substrate layer, etc.

As can be seen from the above embodiments, the use of the applicationsheet 16 containing adhesive dots 13 allows the adhesive-free substrateto be punched or embossed. Thus, preventing or inhibiting the punch dieor embossing machinery from becoming coated and/or contaminated by anyadhesive. Further, utilizing the application sheet 16 and adhesive dots13 allows the adhesive-free first substrate layer and the adhesive-freesecond substrate layer to be attached to one another without the needfor aligning an additional adhesive layer.

The above invention has been further illustrated in connection with aparticular electrochemical test strip. However, the invention is notlimited to this particular type of test strip. The present invention maybe utilized in connection with other embossed or punched test stripsincluding, but not limited to, electrochemical and optical sensors inwhich two or more structures are adhered to each other.

While the invention is susceptible to various modifications andalternative forms, specific embodiments and methods thereof have beenshown by way of example in the drawings and are described in detailherein. It should be understood, however, that it is not intended tolimit the invention to the particular forms or methods disclosed, but,to the contrary, the intention is to cover all modifications,equivalents and alternatives falling within the spirit and scope of theinvention as defined by the appended claims.

1. A method for manufacturing a test strip comprising the acts ofproviding an application sheet having a first surface; printing aplurality of adhesive dots on the first surface of the applicationsheet; providing a plurality of substrate layers having at least oneface; fashioning at least one feature onto a first of the plurality ofsubstrate layers, applying the application sheet to the first substratelayer, the adhesive dots being located between the first surface of theapplication sheet and the first substrate layer; transferring at leastone adhesive dot by removing the application sheet from the firstsubstrate layer; aligning a second of the plurality of substrate layerswith the first substrate layer; and applying the second substrate layerto the first substrate layer, such that the transferred adhesive dotsare in contact with both the first substrate layer and the secondsubstrate layer.
 2. The method of claim 1 further comprising the act ofapplying a silicon coating to the first surface of the application sheetprior to printing the plurality of adhesive dots on the first surface ofthe application sheet.
 3. The method of claim 1, wherein the act offashioning at least one feature is performed by punching the firstsubstrate layer.
 4. The method of claim 1, wherein the act of fashioningat least one feature is performed by embossing the first substratelayer.
 5. The method of claim 1, wherein the act of printing a pluralityof adhesive dots on the first surface of the application sheet occursafter the fashioning of at least one feature onto the first substratelayer.
 6. The method of claim 1, wherein the plurality of adhesive dotsis printed with glue.
 7. The method of claim 1, wherein the manufacturedtest strip is an electrochemical test strip.
 8. The method of claim 1,wherein the manufactured test strip is an optical test strip.
 9. Amethod for manufacturing a test strip comprising the acts of providingan application sheet having a first surface; applying an adhesive to aplurality of different areas on the first surface of the applicationsheet; providing a plurality of substrate layers adapted to form thetest strip, the plurality of substrate layers having at least one face;fashioning at least one feature into a first of the plurality ofsubstrate layers, wherein the at least one feature creates an uppermostsurface and a lowermost surface on the face of the first substratelayer; applying the application sheet to the first substrate layer, theadhesive being located between the first surface of the applicationsheet and the face of the first substrate layer, at least one of theplurality of different areas of the adhesive being in contact with theuppermost surface of the face of the first substrate layer; transferringthe adhesive by removing the application sheet from the first substratelayer after at least one of the plurality of different areas of theadhesive is in contact with the uppermost surface of the face of thefirst substrate layer, such that the adhesive in contact with theuppermost surface of the face of the first substrate layer remains;aligning a second of the plurality of substrate layers with the firstsubstrate layer; and applying the second substrate layer to the firstsubstrate layer, the adhesive remaining on the uppermost surface of theface of the first substrate layer being in contact with both the firstsubstrate layer and the second substrate layer.
 10. The method of claim9, wherein the act of applying an adhesive to the plurality of differentareas on the first surface of the application sheet is performed byprinting the adhesive onto the first surface of the application sheet.11. The method of claim 9 further comprising the act of applying asilicon coating to the first surface of the application sheet prior toapplying the adhesive to the plurality of different areas on the firstsurface of the application sheet.
 12. The method of claim 9, wherein theadhesive applied to the first surface of the application sheet is glue.13. The method of claim 9, wherein the manufactured test strip is anelectrochemical test strip.
 14. The method of claim 9, wherein themanufactured test strip is an optical test strip.
 15. A method formanufacturing a test strip comprising the acts of providing anapplication sheet having a plurality of adhesive dots thereon; providinga first substrate layer having at least one feature located thereon;providing a second substrate layer; transferring at least one of theplurality of adhesive dots located on the application sheet to the firstsubstrate layer; aligning the first substrate layer with the secondsubstrate layer; attaching the first substrate layer and the secondsubstrate layer using the transferred adhesive dots, wherein theattaching of the first and second substrate layers is performed withoutany additional alignment.
 16. The method of claim 15 wherein the act oftransferring the plurality of adhesive dots is performed by applying theapplication sheet to the first substrate layer, such that the pluralityof adhesive dots are located between the application sheet and the firstsubstrate layer, then removing the application sheet from the firstsubstrate layer, such that at least one of the plurality of adhesivedots remains on the first substrate layer.
 17. The method of claim 15wherein the at least one feature of the first substrate layer isfashioned by punching.
 18. The method of claim 15 wherein the at leastone feature of the first substrate layer is fashioned by embossing. 19.The method of claim 15, wherein the plurality of adhesive dots is gluedots.
 20. The method of claim 15 wherein the provided application sheetis a silicon treated application sheet.
 21. The method of claim 15,wherein the manufactured test strip is an electrochemical test strip.22. The method of claim 15, wherein the manufactured test strip is anoptical test strip.